This is a 2 Channel isolated 5V 10A relay module Optocoupler for Arduino PIC ARM. It can be used to control various appliances and other types of equipment with a large current. It can be controlled directly with 3.3V or 5V logic signals from a microcontroller (Arduino, 8051, AVR, PIC, DSP, ARM, ARM, MSP430, TTL logic). This relay has a 1×4 (2.54mm pitch) pin header for connecting power (5V and 0V), and for controlling the 2 relays. The pins are marked on the PCB as: GND – Connect 0V to this pin. IN1 – Controls relay 1, active Low Relay will turn on when this input goes below about 2.0V IN2 – Controls relay 2, active Low Relay will turn on when this input goes below about 2.0V VCC – Connect 5V to this pin. Is used to power the optocouplers Note: This 5V Dual Channel Relay Module is for low level trigger only. About high level and low level-triggered mode: High-level trigger refers to the signal voltage between input and trigger, can be understood as a signal input with VCC cathode short-circuit triggered a way; Low-level trigger refers to the signal voltage between the input terminal and Earth OV trigger, can be understood as the signal input terminal and the GND negative electrode short circuit triggered away 1-channel relay module connection Jumper Instruction = The relay can be turned on when we connect 5v to one end and the other to -5v / Gnd, while talking about the jumper, if we short the VCC and the middle pin, then our relay will act as high level-triggered relay means that when we will apply + 5V input on its input pin it will be turned on and when the jumper will be set to “middle and GND”, it will act as a low-level triggered relay, It means that relay will be triggered when we implement the 5V / GND on its input pin.